The invention has been developed primarily to aid in the disinfection of sensitive fibre optical surgical instruments and will be described herein after with reference to this application. However, it will be understood that the invention is not limited to this particular field of use. For example, the compositions of the invention may be used to clean and sterilize other medical apparatus such as plastic tubing used for supplying medications and nutrients to patients during and following surgery.
One of the unexplained problems of modern surgery where fibre optic endoscope techniques are employed is the incidence of post operative (nosocomial) infections. These infections can usually be traced to a patient who previously had surgery using the same endoscope. This is despite the regular use by hospital staff of methods to clean and disinfect endoscopes thoroughly, using the best chemicals and cleaning techniques recommended by instrument manufacturers and medical microbiologists.
The current protocols for cleaning endoscopes begin with first washing the outside of a freshly used instrument with an enzyme containing neutral detergent. The detergent is then forced into the fine Teflon channels within the larger Teflon tubing of the instrument cover that enters a patient. Then the entire inner surface is carefully brushed in the presence of the detergent. The tubing is then rinsed with water and a disinfectant, either glutaraldehyde, peracetic acid, hydrogen peroxide or a mixture of the latter two. The disinfectant is then forced into the small Teflon channels and the entire instrument is soaked in the disinfectant solution where it remains for a recommended period. The instrument is then scrupulously rinsed with sterile water and dried under asceptic conditions.
There are number of disadvantages with the above recommended techniques. The first is that both glutaraldehyde and peractic acid have obvious well documented safety disadvantages. In addition peractic acid is expensive and destructive to components in the endoscopes. However, the main disadvantage is that recent research within the Medical Department of The University of Sydney has found that viable microbes may still remain on or in an apparatus which has been treated by these methods.
The major finding of the research referred to above was that in use endoscopes often become internally contaminated by bacterial “biofilms”. These are distinctive, unique films deposited on inanimate surfaces by chemicals excreted by bacteria as part of their normal life processes, which serve as a natural protective home for bacteria of all classes. Previously biofilms have been identified and noted visibly or with the use of standard microscopes. However, by using Scanning Electron Microscopy (SEM) the inventor has now identified that the biofilm consists of a number of layers and most importantly there exists a thin layer of biofilm which is adjacent and attaches tightly to the surface of medical apparatus. This thin layer is herein referred to as the “basal layer” and can carry within it and/or associated with it active colonies of vegetative bacteria and blood born viruses such as the AIDS virus (HIV) and hepatitis B (HBV).
Importantly, bacteria and viruses found within biofilms are highly resistant to both chemical disinfectants and antibiotics. See “J W Costerton & P S Stewart, ‘Battling Biofilms’, Scientific American, July, 2001, pages 60-67”. As reported in this paper Bateria located within biofilms can require from 25 to 1500 times the normal quantity of biocides and antibiotics to achieve complete sterilization. Thus, as will be appreciated this can greatly increase the cost of cleaning and wear and tear of the medical apparatus.
For general disinfection purposes it is possible to utilise very strong oxidising agents which can eliminate microbes as part of the disinfectant composition. However, if such agents are used to clean sensitive medical and dental equipment, problems can arise due to the highly corrosive properties of the compositions. Thus for medical and dental equipment and in particular fibre optic endoscopes it is necessary to use less corrosive disinfectant compositions. Although, as explained above, it has been found that adequate cleaning has not been achievable with these compositions. Whilst not wishing to be bound by theory this is thought to be because viable microbes embedded in the basal layer of the biofilm can survive precleaning and disinfecting with oxidising disinfectants, such as peracetic acid, and can become a potential source of post-operative infections.
Known compositions and methods that have been developed to clean and disinfect medical equipment include the use of neutral detergents such as Sonidet (Whiteley Industries Inc) and Endozyme (Davis & GECK Inc). These compositions and methods are generally effective in removing bulk soil and soft biofilm. However, Applicant has determined that these compositions do not remove, or completely kill the all of the viable microbes, in the basal layer of the biofilm.
The inventor has also previously developed a new glutaraldehyde concentrate for use with disinfecting and sterilising fibre optical surgical equipment. This new concentrate is described in international patent application number PCT/AU97/00734 and comprises:                (a) at least one mono or dialdehyde containing two to eleven carbon atoms;        (b) at least one glycol or polyol containing two to ten carbon atoms; and        (c) at least one lithium based buffer soluble in said concentrate capable of maintaining the concentrate at pH 6 or above.        
In this earlier invention the lithium buffer was used to control the pH of both the concentrate and its dilutions to within the desired biocidal effective range, ie at pH 6 or above. However, as noted above the usefulness of the composition of this earlier invention is restricted due to the presence of the glutaraldehyde.
Clearly there is an extensive body of knowledge on detergent processes and chemical disinfectants/sterilants, and application techniques, used in recent times to prevent, control and eliminate biofilms from an array of inanimate surfaces. This, however, is not applicable for totally removing and disinfecting/sterilizing biofilms found in endoscopes, and other more complex surgical instruments. There is thus a clear need for a simple to use, non-corrosive, safe, near neutral chemical detergent compounds that will efficiently and reliably clean and disinfect endoscopes.